stand·by 
(stăndbī′)
(stăndbī′)n. pl. stand·bys
1. One that can always be relied on, as in an emergency.
2. One kept in readiness to serve as a substitute.
3. A mode of operation for a computer, television, or other electronic device in which the power is on and the device is ready for immediate use.
adj.
1. Kept in reserve for use when needed: a standby generator.
2. Of, relating to, or waiting for unreserved travel space that is made available by an airline only shortly before departure: standby passengers.
adv.
Idiom: On a standby basis: flew standby to New York.
on standby
1. Ready and available.
2. As a standby passenger.
- standing-room
- standing stone
- standing wave
- Standish
- stand off
- standoff
- standoffish
- standoffishness
- stand on
- stand (one's) ground
- stand one's ground
- stand on head
- stand on (one's) head
- stand on one's head
- stand on one's own feet
- stand on (one's) own/two feet
- stand on one's two feet
- stand on own feet
- stand on two feet
- stand out
- standout
- stand over
- stand pat
- standpat
- standpatter